Various types of batteries have been developed heretofore, and in every battery, a packaging material is an essential member for sealing battery elements such as an electrode and an electrolyte. Metallic packaging materials have been often used heretofore as battery packages, but in recent years, batteries have been required to be diversified in shape, and desired to be thinner and lighter as performance of, for example, electric cars, hybrid electric cars, personal computers, cameras and mobile phones has been enhanced. However, metallic battery packaging materials that have often been heretofore used have the disadvantage that it is difficult to keep up with diversification in shape, and there is a limit on weight reduction.
Thus, in recent years, a film-shaped laminate with a base material layer, a metal layer and a heat-sealable resin layer laminated in this order has been proposed as a battery packaging material which is easily processed into diversified shapes and is capable of achieving thickness reduction and weight reduction (see, for example, Patent Document 1). In such a battery packaging material, generally, a concave portion is formed by cold molding, battery elements such as an electrode and an electrolytic solution are disposed in a space formed by the concave portion, and heat-sealable resin layers are heat-welded to obtain a battery with battery elements stored in the battery packaging material.
For obtaining a battery packaging material having excellent moldability, an aluminum foil is widely used as a metal layer in such a film-shaped laminate.